1. Field of the Invention
This invention relates to mutilayer oxygen barrier pac aging for refrigerated or shelf stable microwave applications and, more particularly, relates to multilayer packaging having a supporting layer made from a blend of polyphenylene ether and high impact polystyrene.
2. Description of Related Art
Multilayer structures for use as packaging materials for storing foods have been known for some time. See, for example, Giles, Jr., et. al., U.S. Pat. No. 4,734,331, which discloses multilayered structures comprising at least one polycarbonate layer, at least one ethylene-vinyl alcohol copolymer layer, at least one polyolefin layer and suitable tie layers disposed between the layers to provide compatible adherence therebetween. Each layer provides the structure with desirable properties lacking in the other layers, for example, the polycarbonate layer provides the layer with heat resistance and impact resistance, the olefin vinyl alcohol copolymer layer provides the structure with oxygen barrier properties for inhibiting food spoilage, and the polyolefin layer acts as a water barrier. Although the employ of a polycarbonate layer in the aforementioned structure provides the structure with improved impact strength it may prove to be less cost effective than other alternatives. For example, high impact polystyrene layers have been employed in the past in similar multilayer structures for the purpose of cost effectively providing adequate mechanical properties to the structure. High impact polystyrene layers have, however, been found to generally lack the desired level of heat resistance necessary for microwaveable food packaging and some hot filling processes commonly used in the food industry. Specifically, outer layers of high impact polystyrene tend to exhibit burn through or distortion when adjacent to heat concentrating dense food portions, liquids or high grease or oil based foods during microwave or conventional oven cooking, reheating or high temperature sterilizing of foods resulting in the food items effectively burning through, melting or distorting the layer or layers resulting in either contamination of the food with melted resin or distortion of the package thereby leading to customer dissatisfaction.
Accordingly, one object of the present invention is to provide a multilayered structure for packaging that overcomes the foregoing thermal deficiencies of prior structures while retaining the desirable package forming qualities of high impact polystyrene.